Spectroscopic measurements have been widely applied to address many different purposes such as medical diagnostics, industrial process control and forensic measurements. In many of these applications the sample of interest is brought to a laboratory or clinical facility where the spectrometer is located. This allows one spectrometer to measure samples acquired in multiple locations. Recently, the evolution of spectroscopic instrumentation has given rise to the desire to measure samples from multiple locations simultaneously without transporting them to a dedicated facility. This is particularly important in applications such as in vivo medical or forensic tests where transporting the subject to a measurement facility may not be feasible or in process control where real-time measurements are critical and the delays caused by sample transportation are not acceptable. As such, these applications can require multiple spectroscopic devices at one or more locations.
There are two significant consequences of the transition of spectroscopic devices away from the laboratory and to the location of the sample that are related to the present invention. First, the location of the sample is typically an environment that has a large range of potential perturbations (e.g. vibrations of a factory floor, temperature range for outdoor measurements) relative to the carefully controlled conditions typically observed in a laboratory or clinical facility. Second, when multiple spectroscopic devices are located in one or more facilities, the range of environmental conditions can vary significantly between the sites. Consequently, any type of spectroscopic device deployed in such conditions must be designed to mitigate or compensate for environmental disturbances that have been largely limited in laboratory applications of spectroscopy.
The present invention is related to the mitigation of environmental disturbances of spectroscopic devices (spectrometers) incorporating interferometers and compensating for differences between such spectroscopic devices deployed to one or more locations. Some common examples of spectrometers that can incorporate interferometers are visible, NIR, and IR absorption spectrometers; visible: NIR, and IR emission spectrometers; and Raman spectrometers. One skilled in the art recognizes that other applications of interferometric spectroscopy exist that could benefit from the present invention. There are many different types of interferometer designs and architectures recognized in the art that could benefit from the present invention. Some examples include Michelson, Mach-Zehnder, and refractive interferometers. For demonstrative purposes the remainder of this disclosure will discuss embodiments of Fourier Transform Near infrared (FT-NIR) spectrometers using a Michelson geometry interferometer and is not intended to limit the scope of the present invention.